Shock absorbers are used in vehicles such as automobiles, motorcycles, bicycles, farm equipment, trucks and aircraft to improve the ride, handling or landing characteristics of such vehicles. A vehicle suspension system enables a wheel to travel with respect to the frame to provide cushioning and absorb shock. A shock absorber provides damping to this movement to help to reduce the velocity of these movements.
Typically, a shock absorber comprises a cylindrical housing having a piston contained therein. In some shock absorbers, the piston has a head, and fluid (liquid or gaseous) is placed within the interior of the shock absorber housing on both sides of the piston head. The piston head may contain one or more valve members that can be as simple as apertures that extend through the piston head.
As the piston head moves axially within the cylindrical housing shaft, fluid is moved from one side of the piston head to the other side of the piston head by traveling through the valve (e.g. the apertures that extend through the piston head). Because the fluid must pass through the valve or holes, the speed of the piston's axial movement is reduced or “damped” as it moves axially within the cylindrical housing. The restriction of fluid caused by the valves impedes the movement of the piston and thus serves to serve to slow the speed of the travel of the piston. Alternately, a solid head piston can be employed, and a separate valve system be used.
It is possible to control the amount of damping force by varying the size of the orifice in the valve that controls the rate at which the fluid can flow from the first reservoir on one side of the piston, through the piston head and to the reservoir on the other side of the piston.
It has been found and has been known that one can adjust the size of valve opening to achieve different damping forces. For example, if a relatively small damping force is desired, one would allow the valve to have a relatively large orifice to thereby allow a relatively high rate of fluid to pass through the valve. Such a low damping force would cause relatively less impedance of the piston's ability to move axially within the cylindrical shock absorber housing and therefore provide less impedance to the velocity of the travel of the wheel relative to the frame. A relatively low damping force would tend to provide a relatively “softer”, less choppy ride for the vehicle.
On the other hand, increasing the damping force provides for a “stiffer”, more choppy ride by providing for slower travel of the wheel and piston within the cylindrical housing by providing the piston (or other valve) with a smaller orifice that thereby decreases the rate at which fluid is able to flow through the piston.
There are certain times when one desires to vary the damping of a particular shock absorber that is mounted on a vehicle, so that the shock absorber itself can be “tuned” and varied between a relatively high damping force and a relatively low damping force. One instance where this occurs is in connection with mountain bicycles and off-road motorcycles.
A mountain bike rider often wishes to vary the damping force to better match the conditions of the particular trails on which she is riding and the direction and speed at which she is traveling on a trail. For example, unless the rider is looking for extreme comfort, the rider should set the shock absorber to have a relatively high damping force (relatively greater resistance to movement) when the rider is on a relatively smooth riding surface since a stiffer ride allows the bicycle to operate more efficiently.
Cyclists on mountain bikes also often desire to employ a relatively high damping forces when riding a bicycle uphill. When the rider is riding uphill, he is typically traveling at a relatively slow rate, when compared to the speed at which the rider rides downhill. Therefore, when riding uphill, most riders seek to have a relatively higher damping force and higher efficiency, as they are not as concerned about making the bumps softer.
However, high damping forces are not as desirable when the rider is traveling over an extremely rough surface or when the rider is riding downhill. When the rider is riding downhill, she hits bumps and obstacles at a higher speed, that thereby induce greater impacts on the bike, and greater “shocks” on the rider and the bike. To help reduce this heightened shock and force, the user can decrease the damping force so that the wheels may travel relatively further (when the same force is applied to the wheel), and with less resistance when compared to when a high damping force is utilized.
Viewed another way, a bike is generally more efficient when the damping force is increased. The higher efficiency occurs because the movement of the rider when turning the pedals and crank (especially when doing so vigorously), and moving his weight on the bike can cause rider-induced suspension movement. This rider-induced suspension movement lowers the efficiency of the bicycle, as it decreases the amount of power transmitted to the wheels for a given amount of force to the pedals applied by the rider.
However, on a downhill run or rocky terrain, the suspension induced movements are likely to be less of a factor because the rider is less likely to be as vigorously pounding on the pedals to move the bike. Additionally, the desire to absorb the forces caused by the rocks, fallen trees and other obstacles hit by the bicycle at higher speeds when going downhill often outweighs the benefits of increased efficiency.
Preferably, the rider can adjust the damping force during a particular ride. It would therefore be useful to provide a device that enables the rider to adjust the shock absorber's damping force. Currently, such adjustability exists, but is limited.
One known adjustable shock absorber provides dials on the shock absorber that enable the user to adjust the dials to achieve his desired damping force. Unfortunately, the use of this particular device has significant drawbacks. In particular, the rider is usually required to stop riding long enough to adjust the dials to vary the damping. This required stop and/or the difficulty that exists to change the dial which riding costs the rider valuable time and therefore is undesirable to competitive riders.
Therefore, one object of the present invention is to provide the rider with a damping force controller that permits the user to make “on the fly” adjustments to the compression damping force.
Another difficulty experienced with known prior art adjustable damping systems is that even though prior art shock absorbers were adjustable between a “relatively stiff” and “relatively loose” (or relatively high damping compressive force and relatively low damping compressive force) positions, the high and the low settings were coupled to each other so that one could not adjust the compressive force when in the high compressive force range independently from the force at the low compressive force range. This coupling occurs because the known prior art devices use a single valve.
In order to move the valve from the high compressive force range to the low compressive force range, known devices employed a bypass path that was selectively opened to provide a second path for the fluid to flow from one side of the valve to the other. The second fluid path is in addition to the first, primary through-the-valve path that is open all the time, both during the high compressive force setting and in the low compressive force setting. During the high compressive force setting, the bypass valve is closed. When the user desires to move the valve to the lower compressive force setting, the user opens the bypass valve to provide a second fluid flow path and hence provide for a greater flow rate capacity.
Typically, known bypass valves have a non-adjustable, fixed size that permit a fixed fluid flow rate to flow through the bypass valve when the bypass valve is opened. As such, the combined fluid flow through the valve when adjusted into the low compressive force setting equals the flow rate through the first valve, flow path plus the flow rate through the second flow path provided by the bypass.
As such, if one adjusts the flow rate through the first, primary valve so that the valve is set to provide a very high compressive force to thereby provide a very “stiff” suspension, opening the bypass valve will provide a relatively looser spring or lower compressive force. Nonetheless, the combined lower compressive force would still result in a relatively stiff lower compressive force because the combined flow through the primary and bypass valve would still be relatively low because of the low fluid flow rate through the primary valve. In particular since the setting of the primary compression force valve has not and cannot not be) changed from its “stiff” setting, the fluid flow contribution from the primary value is relatively low and the combined fluid flow from both the primary and bypass valves is still relatively low.
As such, the overall effect of such an arrangement is to provide the shock absorber with a relatively high compression damping force, even though the shock is set in the low damping force range. When so set, the bike will have a ride, that while “softer” than when in the “high compression force” setting, is still relatively stiff. Such a ride is characterized as having a “low bump sensitivity”. Low bump sensitivity generally refers to a condition where because of the stiffness of the spring, the wheel and shock absorber do not move much when the wheel hits a small obstacle, such as a twig, rock or the like, that generally leads to a relatively uncomfortable but efficient ride.
On the other hand, if the user wanted a more comfortable ride when in the lower damping setting, he would employ components that created a compressive force of the primary valve that was designed to achieve at a relatively lower damping force. Although this arrangement provides the user with increased “bump sensitivity” and a softer ride, it also provides the user with a softer ride when the bypass valve is closed because the primary compressive valve is still set to allow more fluid to flow there through, when compared to when the valve is set at a relatively higher compressive force rate. As such, in order to achieve a softer ride downhill, the user has to endure a softer, less efficient ride uphill.
In summary, the known prior art devices are not readily capable of allowing the user to adjust the uphill and downhill compressive forces of the shock absorber independently of each other, since the mechanisms are tied together. As such, the compressive force of the uphill setting and downhill setting are dependent upon each other.
One object of the present invention is to provide a device that allows the uphill compressive force setting to be adjusted independently of and not be dependent upon, the adjustment of the downhill damping compressive force.